Systematic ARPES study on Na-rich Na$_{x}$CoO$_{2}$ (0.75$<$x$<$1)

The phase diagram of the cobaltite Na$_{x}$CoO$_{2}$, with varying Na concentration x, is very rich and complicated. At the high-doping regime (x$>$0.75), the system was found to be more correlated, with a spin-density-wave state emerging at low temperatures. A stable phase was found with $\sqrt {13} \times \sqrt {13} $ symmetrical superstructure at Na-rich doping cobaltite. We will report our recent ARPES results of the Na-rich Na$_{x}$CoO$_{2}$ (0.75$<$x$<$1) samples.